Amorphous Material Content Research Articles

Impact of different metakaolin mixtures on oligomer formation and geopolymer properties: Impurity effect

The impact of metakaolin mixtures on geopolymer formation and corresponding properties was evaluated by synthesizing geopolymers from mixtures of different metakaolins and 5 M potassium silicate. Mixture reactivity was investigated by viscosity, thermogravimetric (DTA-TGA), and in situ infrared spectroscopy (FTIR) measurements. Furthermore, mechanical strength and porosity measurements were undertaken on consolidated materials. The results have shown that the aluminum molar concentration governs the setting time and oligomer formation energy. Indeed, the high aluminum content associated with the high purity of the metakaolins lead to a low formation energy of oligomer, whereas for the metakaolins containing more impurities, the energy required for oligomer formation was higher. Regardless of the formulation, the mechanical strength and porosity trends were similar. Network characteristics were assessed by amorphous material content and in situ infrared spectroscopy (FTIR) analysis. It was demonstrated that (i) for Si/Al < 1.5, an amorphous network is formed with a constant Si/Al ratio, and for (ii) Si/Al > 1.5, different networks are formed. The zeta potential values of the different metakaolin mixtures corroborated these findings. Zeta potential values of metakaolins are governed by the impurities present in the metakaolins, which limit the release of aluminous species from the metakaolins in solution, emphasizing that knowledge of raw materials is essential to understand the local networks formation.

The mineral evolution during coal washing and its effect on ash fusion characteristics of Shanxi high ash coals

Gasification has been deemed as the most promising method for the thermochemical conversion of Shanxi high ash coals, although the use of these high ash coals leads to high consumption of coal and oxygen, low syngas yield and cold gas efficiency. In order to improve gasification efficiency, it is necessary to reduce the ash content of these Shanxi high ash coals. In this work, three representative Shanxi high ash coals were floated with ZnCl2 flotation agent to obtain floated coal samples with different ash contents. The mineral evolution during coal washing and its effect on ash fusion characteristics were thoroughly investigated. A radio frequency oxygen plasma furnace, X-ray diffraction (XRD) and SIROQUANT were used to analyze the variation of mineral compositions of the floated coals. Quartz (SiO2), kaolinite (Al2(Si2O5)(OH)4), calcite (CaCO3), and tobelite (NH4Al3Si3O10(OH)2) were main mineral which were found in Shanxi high ash coals, and the high contents of quartz and kaolinite led to high AFTs (ash fusion temperatures) of these coals. As mineral content decreased, the contents of quarts, kaolinite, and calcite in the floated coals were obviously lowered, and this resulted in the decrease of S/A (mass ratio of SiO2/Al2O3) of the coal ashes. The ash fusion temperatures of Shanxi high ash coals were therefore significantly influenced by the extent of coal washing. Furthermore, the content of amorphous material in coals increased obviously with the decrease of ash content. These results have important implication in the selection of the appropriate coal washing procedure prior to gasification of these coals.

SOIL PROPERTIES OF THE EASTERN TOPOSEQUENCE OF MOUNT KELIMUTU, FLORES ISLAND, EAST NUSA TENGGARA AND THEIR POTENTIAL FOR AGRICULTURAL USE

Kelimutu stratovolcano is one of the young volcanoes extensively found in Flores island. Studies on volcanic soil properties and their suitability for agricultural development in the whole island are lacking. The research was conducted to evaluate the relationship of elevation and soil properties, and suitability for agricultural development. Five representative pedons at elevation of 550, 1,000, 1,200, 1,400, and 1,600 m above sea level (asl), respectively, were studied in the field, and 22 soil samples were analyzed in the laboratory. The results indicated that elevation significantly affected soil properties and degree of soil weathering. With decreasing elevation, sand content, amorphous material content, and phosphate retention decreased. Concomitantly, clay content, H2O-pH, exchangeable Ca and Mg, base saturation, and soil-CEC increased. A highly positive correlation was shown between P retention and NaFpH, Al, and (Al+0.5 Fe) contents extracted by acid ammonium oxalate. Soil-CEC also showed significant positive correlation with clay and silt contents, organic carbon, and exchangeable Ca and Mg. Degree of weathering increased with decreasing elevation as reflected by decreasing silt/clay ratio. Soils developed from Entisols (Lithic Udorthents) at 1,600 m asl, to Andisols (Typic Hapludands) at 1,000-1,400 m asl, and Mollisols (Typic Hapludolls) at lower elevation down to 550 m asl. Soils at 1,400-1,600 m asl are unsuitable for agriculture. Soils at 1,000-1,200 m are moderately suitable for food crops, horticulture, and estate crops. Dominant limiting factors are steep slopes and P retention. Soils at 550 m asl are suitable for food and estate crops, and also lowland horticulture.

SOIL PROPERTIES OF THE EASTERN TOPOSEQUENCE OF MOUNT KELIMUTU, FLORES ISLAND, EAST NUSA TENGGARA AND THEIR POTENTIAL FOR AGRICULTURAL USE

Kelimutu stratovolcano is one of the young volcanoes extensively found in Flores island. Studies on volcanic soil properties and their suitability for agricultural development in the whole island are lacking. The research was conducted to evaluate the relationship of elevation and soil properties, and suitability for agricultural development. Five representative pedons at elevation of 550, 1,000, 1,200, 1,400, and 1,600 m above sea level (asl), respectively, were studied in the field, and 22 soil samples were analyzed in the laboratory. The results indicated that elevation significantly affected soil properties and degree of soil weathering. With decreasing elevation, sand content, amorphous material content, and phosphate retention decreased. Concomitantly, clay content, H2O-pH, exchangeable Ca and Mg, base saturation, and soil-CEC increased. A highly positive correlation was shown between P retention and NaFpH, Al, and (Al+0.5 Fe) contents extracted by acid ammonium oxalate. Soil-CEC also showed significant positive correlation with clay and silt contents, organic carbon, and exchangeable Ca and Mg. Degree of weathering increased with decreasing elevation as reflected by decreasing silt/clay ratio. Soils developed from Entisols (Lithic Udorthents) at 1,600 m asl, to Andisols (Typic Hapludands) at 1,000-1,400 m asl, and Mollisols (Typic Hapludolls) at lower elevation down to 550 m asl. Soils at 1,400-1,600 m asl are unsuitable for agriculture. Soils at 1,000-1,200 m are moderately suitable for food crops, horticulture, and estate crops. Dominant limiting factors are steep slopes and P retention. Soils at 550 m asl are suitable for food and estate crops, and also lowland horticulture.

Alkali Activation–Granulation of Hazardous Fluidized Bed Combustion Fly Ashes

The increasing amount of fluidized bed combustion (FBC) ash is putting pressure on researchers to invent novel methods for utilizing the ash. The low reactivity and heavy metal content constrict the use of FBC ash in the same way as coal ash from pulverized combustion. Four FBC fly ashes from different power plants were granulated with sodium silicate solution in order to produce artificial aggregates. All aggregates matched the definition for lightweight aggregate according to the EN 13055-1 standard. The strongest aggregates were produced from fly ashes that had the highest X-ray amorphous material content and the highest amount of selectively soluble SiO2 and Al2O3. However, the same leaching problem (leaching of the anionic species) as with coal fly ashes was observed with the FBC fly ashes. The simultaneous high shear granulation and alkali activation of FBC ashes showed that artificial aggregates with satisfactory physical properties, such as density and strength, can be obtained even from low-reactive fly ashes that contain heavy metals.

Enzymatic surface modification of sisal fibers (Agave Sisalana) by Penicillium echinulatum cellulases

We report on the effect of a new microbial enzymatic system, Penicillium echinulatum cellulase, on the surface morphological (SEM), structural (XRD), and thermal (TGA/DTG) properties as well as the surface chemical composition (FT-IR and FT-Raman) of sisal fibers (Agave sisalana)—a potential replacement for glass fibers in composite materials. Cellulase treatment greatly improved the properties of sisal fibers, rendering the surface topography and chemical composition of the fibers free of contaminants and reducing the content of amorphous materials (hemicellulose, pectin, lignin, and disordered cellulose) to yield the crystalline cellulose network. Thermal stability and crystallinity were also greatly enhanced. This work demonstrated that microbial enzymes offer an inexpensive and environmentally attractive option to improve the surfaces of natural fibers for composite applications.

Comparison of chemical reactivity of bauxite-tailings pre- and post-calcinations and whitening bauxite-tailing

Bauxite-tailings is aluminosilicate wastes and is used in polymer as fillers. But its intrinsic low-whiteness has limited its large-scale application in polymeric materials. Conventional methods for whitening bauxite-tailings were ineffective. A new method, which involved reactions with phosphoric acid and calcinations, was proposed to whiten bauxite-tailings. Two process routes were employed to whiten bauxitetailings, which were pre- and post-reaction calcination. While the process of pre-reaction calcination was able to achieve a whiteness of 87% from bauxite-tailings, it required high-energy post-treatment processes such as washing, milling and drying. The process of post-reaction calcination, on the other hand, resulted in an increase in whiteness of bauxite-tailings from 19% to 73%. This was achieved using 4.5% of added phosphorous, 40% acid concentration, reaction time of 2.5 hours and a calcination temperature of 600 °C. The resultant did not require any further processing, and was therefore industrially feasible. The whitened tailings consisted of corundum, anatase, and quartz. When compared to calcined tailings, whitened tailings possessed a higher content of amorphous material, the disappearance of red iron minerals, and the emergence of a new phase of AlPO4.

Mineral behavior of low-temperature lignite ashes under gasification atmosphere

To investigate the mineral behavior of lignite ashes under gasification conditions, 450 °C Xiaolongtan lignite ash samples (XLT-LTA) treated at different temperatures or pressures under reducing atmosphere (H2/CO2=1: 1, volume ratio) have been examined by means of an SC-444 apparatus, a scanning electron microscope with an energy dispersive X-ray detector (SEM-EDX), and by X-ray diffraction (XRD). The results showed the sulfur content in the XLT-LTA to be much higher than that in ashes prepared at 815 °C, as a result of the release of sulfur dioxide during the oxidization of pyrite. With increasing temperature, the XLT-LTA particles gradually agglomerate and form partially molten surface entities with obvious apertures, and the content of iron and calcium in the congeries or molten parts increases due to the fusion of fine ash particles with the enrichment of iron and the formation of low-temperature eutectics of calcium and iron. An increase of pressure restrains the decomposition of calcite and muscovite, and promotes the formation of iron minerals (e.g., hercynite, cordierite, and sekaninaite) and orthoclase. The content of amorphous material also increases with increasing pressure.

Re-use of drinking water treatment plant (DWTP) sludge: Characterization and technological behaviour of cement mortars with atomized sludge additions

This paper aims to characterize spray-dried DWTP sludge and evaluate its possible use as an addition for the cement industry. It describes the physical, chemical and micro-structural characterization of the sludge as well as the effect of its addition to Portland cements on the hydration, water demand, setting and mechanical strength of standardized mortars. Spray drying DWTP sludge generates a readily handled powdery material whose particle size is similar to those of Portland cement. The atomized sludge contains 12–14% organic matter (mainly fatty acids), while its main mineral constituents are muscovite, quartz, calcite, dolomite and seraphinite (or clinoclor). Its amorphous material content is 35%. The mortars were made with type CEM I Portland cement mixed with 10 to 30% atomized sludge exhibited lower mechanical strength than the control cement and a decline in slump. Setting was also altered in the blended cements with respect to the control.

Natural mixture of silica and smectite as a new clayey material for industrial applications

AbstractThe main physico-chemical properties of a new smectitic clay containing large amounts of amorphous material are reviewed and potential industrial applications of this type of clay are discussed. Due to a 34% amorphous material content (natural silica gel), the investigated clay has very high porosity and can be used as it is or in acid-impregnated form for oil bleaching or phosphate reduction in edible oil. In the field of biodiesel purification, the new clay can be used to remove, in particular, mono-, diglycerides and glycerol. The natural silica-smectite mixture is also suitable as a carrier for liquid ingredients, for example in animal feeds, and might serve as a partial or complete substitute for synthetic precipitated silicas. In the field of bioseparation processes, the clay can be used as an adsorbent for protein separation by means of cation exchange. Due to the suppressed swelling (compared with smectite alone), it can be packed in columns which can be regenerated.

Investigation of the uptake ability of fly ashes produced after lignite combustion

Fly ash samples from the five steam electric power stations of the Lignite Center of Western Macedonia were used in this study. They consisted mainly of anhydrite, lime, quartz and amorphous material as well as feldspars, calcite, micas+clays, portlandite and gehlenite which were all present in minor amounts. Anhydrite, lime and portlandite in the fly ash samples diminished upon treatment with ammonium acetate aqueous solution, whereas quartz, feldspars, gehlenite and amorphous material were enriched. The uptake ability of the fly ash samples ranged from 89 to 101 mequ./100 g. The uptake ability of the samples was mainly attributed to the amorphous material and the microporous minerals, micas+clays. The amorphous material content was estimated at between 17 and 20 wt% in the treated fly ashes and may be unburned organic matter and amorphous inorganic material that resulted during the combustion of the lignite. A positive correlation was observed between the uptake ability and the total percentage of amorphous material and micas+clays. The relatively high uptake ability of the fly ash samples could lead to additional industrial and environmental uses of the fly ashes. The environmental advantage of fly ash exploitation will be particularly important for large electric power centers, such as the LCWM.

The Role of Amorphous Material in Ash on the Agglomeration Problems in FB Boilers. A Powder XRD and SEM-EDS Study

Bed agglomeration is one of the most common problems in FB boilers. In this work the dependence of agglomeration tendency of peat and biomass ash on the content of amorphous material in ash has been investigated. The factors affecting the interactions between quartz bed particles and ash-forming elements have been modeled by involving mixtures of oxides that are commonly found in ash by utilizing X-ray powder diffraction for a semiquantitative determination of amorphous phases and SEM-EDS for compositional distributions. It is well-known that high iron or alkali metal contents increase the agglomeration tendency of ash. It can indeed be seen that the amount of amorphous material in ash increases with increasing iron or alkali metal contents. The results have been compared with those of two standard peat ashes, one of which is known to be unproblematic, while severe agglomeration has been observed in the case of the other.

Physical, chemical, and mineralogical properties of Mexico City sediments: a geotechnical perspective: Discussion

The Authors’ paper presents interesting results from mineralogical tests conducted on the sediments beneath Mexico City. From the title, it could be inferred that the paper would lend some quantitative insight into the reasons for the dis tinctive geotechnical behaviour of the Mexico City sediments. Valuable profiles of the mineralogy, index tests, shear wave velocity, grain-size distribution, and a cone penetration test log are provided; however, it appears that no attempt has been made to quantitatively link the observed “fascinating” behaviours with the presented data if any such links exist. Rather, it is stated that “...results from the present study sug gest that the exceptional properties of Mexico City sediments (i.e., very high water content and plasticity, low shear wave velocity, and remarkable elastic behaviour) are associated with the presence of amorphous material coating the particles.” The authors attribute considerable importance to “amorphous” materials, i.e., noncrystalline oxides of various minerals (principally iron, aluminum, and silicon), in the formation of the Mexican sediments and their observed behaviours. Yet, the processes by which the amorphous material content is determined (Segalen 1968) are chemically aggressive (Bentley 1980; Quigley 1980; Torrance 1995) and could also strip away any carbonate minerals that represent up to 30% of the Mexico City soil mineralogy. The sediments within zone 4 are noted to exhibit considerably different behaviours than those in zones above or below. Of the mineralogical, index-property, and grain-size data presented, it is the differences in calcite, cation exchange capacity, and organic matter which are most characteristic of zone 4 when compared with other zones. It is of interest to compare the Mexico City sediments with illitic sensitive clays in Canada, the United States, and Norway and published data from Fucino, Italy. The Discussers have found interesting correlations between the carbonate content and vertical effective yield stress (preconsolidation pressure) of glacially derived fine-grained soils of New York State and southern Ontario (Boone and Lutenegger 1997). Burghignoli et al. (1991) concluded that carbonates play a role in the observed initial shear modulus, shear wave velocity, and undrained shear strength of the Italian clay and that the influence of carbonate bonding was likely “obliterated” by the large strains involved in penetra tion testing. The sedimentary environment and typical index and mineralogical properties of some of these soils are compared in Table 1. Several differences are striking, namely, (1) The Scandinavian and North American soils were deposited relatively rapidly during retreat of the ice sheets in the last ice age (from approximately 11 000 years before present), whereas those of Italy and Mexico City are reported to have been deposited over a significantly longer period of time (from approximately 64 000 and 600 000 years before present, respectively), i.e., sedimentation rates were likely half an order of magnitude or more slower for the Italian and Mexican deposits. (2) Both the Fucino and Mexico City lacustrine basins were without an outlet for the majority of the inferred sedimentation period. What role might dissolved salts or other minerals within the water body or in the pore water have on the final structure and behaviour of the sediments? Despite many years of research into the effects of salinity on the formation and resultant behaviour of natural sediments, related issues were not discussed in the paper.

石炭灰の蒸気処理による固化・安定化に関する研究

Fundamental study was carried out in order to make use of coal ash as a ground material in large quantities. A series of examination were done by using three kinds of coal ash produced from boilers of which the combustion system differs each other. The properties of coal ash and the characteristics of solidification and stabilization in the solidified coal ash by steam treatment were examined. The main results obtained were as follows:(1) A solid state reaction takes place between coal ash and CaO at the boiler temperature, generating a large amount of hydraulic substances. The morphology of each particle and the content of amorphous materials in coal ash differ depending upon chemical composition, temperature and pressure in the production atmosphere.(2) As coal ash, particles becomes denser or amorphous materials become larger in quantity, the compressive strength of the solidified coal ash becomes higher.(3) The solidified coal ash satisfies a safty standard in leaching by treating it with a saturation steam of proper condition.

Thermal study of an aged dredged sludge

A dredged sludge was studied to investigate the influence of ageing and of pretreatment on its drying rate, water sorption/retention, thermal mass loss, XRD and microstructure (SEM). Ageing caused change in particle thickness and specific surface, a gradual aggregation to form units of the size 10–50 μm, formation of macropores of similar size, unhomogeneity and fissures between aggregates and “super-aggregates”. Macropores were detectable by the initial drying rate especially at 45°C. They indicated a tendency of collapsing at a lower drying rate at 30°C. This is consistent with SEM observations. With ageing the aggregates were more compact and less sensitive to drying. The aggregated system indicated a higher initial drying rate (higher permeability), whereas stirring induced a lower drying rate, favouring the formation of compact laminar structure. XRD peak intensity was lowered with ageing due to decrease in crystallinity (stacking faults and/or decrease in crystallite size). The content of amorphous material was lowered as well, reducing water sorption/desorption, which indicated that the specific surface is lower. From the suitable microstructure induced by ageing some new phases may form (feldspar, zeolites), preferably in the coarser fraction of the sludge. This is disturbed by stirring which operation expels also carbonates from the particle edges and this may reduce the structural strength of the sludge. In aged bentonite suspension a similar tendency was observed of formation of specific microstructures capable of phase transformation, e.g. to feldspar.

Some electrokinetic behaviour of tin tailing slimes

Tin tailing slimes from three ex-mining ponds located in different parts of Malaysia and with different clay compositions were studied. Pengkalan slime contained about 8% of montmorillonite clay; Serendah (SH) slime had a high content of amorphous materials (24%) while the main constituents of all samples were kaolinite and illite with a small amount of organic materials and microorganisms as exemplified by Malim Nawar slime. The surface nature of the clay minerals in these slimes was characterised using the particle microelectrophoresis technique. The electrokinetic behaviour of the slime basically followed that of kaolinite but differences due to compositional variations were evident. This is especially so for the SH slime where the amorphous materials present completely modified the surface property of the kaolinite. The magnitude of the electrophoretic mobility depended strongly upon the exchangeable cations associated with the clay particles and pore fluid chemistry of the slime samples. The evaluation of the isoelectric point of the edges of clay particles by the electrokinetic method is discussed. The importance of understanding the charged surfaces of the clay minerals in the slimes in relation to the design of an efficient dewatering programme is briefly discussed.

Spectral‐chemical analysis of lunar surface materials

Samples of lunar rocks and soils that have been examined in the laboratory both spectroscopically and chemically were analyzed with the goal of identifying and quantifying correlations between reflectance spectra and compositional properties of lunar materials. The method used to quantify spectral variations within the set of spectral samples is principal component analysis. The correlations between the chemical analysis of lunar samples and their spectral quantities are determined by using multivariate analysis. The combination of both methods yields functional relationships between the principal axes of variation and the chemical constituents, in particular, FeO, TiO2, SiO2, Al2O3, MgO, CaO, and MnO, and with the content of amorphous materials (glass) in lunar samples. To first order, the nature of these relationships is found to be linear. The results define a spectral‐chemical model that is applicable to derive abundances of chemical constituents and amorphous components from individual spectra. The accuracy of the model is better than ±2.4 wt % and ±4% for chemical constituents and amorphous components, respectively, making the model also sensitive to remotely sensed spectra of the lunar surface.

まさ土の非晶質物質特性と石灰処理効果

The purpose of this study is to clarify the relationship between the degree of weathering and the content of amorphous materials and the influence of amorphous components on the lime stabilization of the soil from the physico-chemical point of view.The ignition loss and the specific surface area which have been adopted as a criterion of the degree of weathering are related closely to the ratio of Al2O3/SiO2. This fact means that the ratio can be also used as a criterion of the degree of weathering from the chemical point of view.In conclusion, the ratio of Al2O3/SiO2 and lime content have a decisive effect on the unconfined compressive strength of the sample stabilized with lime.

Volcanic Ash‐influenced Vertisols and Associated Mollisols of El Salvador: Physical, Chemical, and Morphological Properties

AbstractVertisols and Mollisols have developed from Quaternary pyroclastic deposits in central El Salvador under ustic moisture and isohyperthermic temperature regimes. Pellusterts generally occupy the nearly level constructional landforms (alluvial plains, coastal plains, and concave alluvial toeslopes), are poorly drained and exhibit darkgray to black colors. Chromusterts and Pellusterts with argillic horizons and secondary silica in lower sola occupy more sloping, erosional upland landforms that are better drained. Associated Argiustolls have formed in loamy or clayey andesitic alluvium on nearly level alluvial plains. Vertisols of El Salvador have many properties in common with Usterts of the USA, i.e., high clay contents, slickensides, tilted parallelpipeds, and deep wide cracks that extend to the surface, but they lack gilgai relief, cyclic horizonation, and with a few exceptions, self‐mulching surface horizons. Most have cambic horizons. The amorphous material content of the &lt;2 µm fraction of these soils range from 14 to 28%, pH's range from 5.4 to 7.5, base saturation is &gt;50% (commonly &gt;75%) with Ca and Mg dominant. COLE values are 0.06 to 0.24 and clays are smectitic or kaolinitic. Microfabrics indicate high shrink‐swell. Stress‐oriented plasmic fabrics are largely vo‐masepic, vo‐skel‐masepic and lattisepic for cambic and Bt horizons indicative of microshear failure. Undulic plasmic fabrics dominate in pumice‐rice ash mantles and pyroclastic‐rich parent materials. Illuvial channel ferri‐argillans and organo‐argillans occur in subsoils of the Chromusterts and Argiustolls, respectively. Pedogenesis and plasmolysis increase in the order: andesitic bedrock or alluvium, saprolite (from bedrock), clay‐enriched Bw and Bt horizons, and Bw horizons in upper sola with slickensides and stress‐oriented plasmic fabrics. The best Bt and silica‐enriched (Bq) horizons occur in lower sola below the more physically active upper Bw horizons.

Quantitative mineralogical analysis of some Bangladesh soils with X-ray, ion exchange and selective dissolution techniques

AbstractFine clay, coarse clay, and silt fractions of four Bangladesh soils were studied using XRD, ion exchange, and selective dissolution techniques. Constants for the XRD intensity-weight proportion relationships were derived using these techniques. Smectite and mica were found to be dominant in Batra and Ghior soils, whereas kaolinite and mica were dominant in the Naraibag and Ghatail soils. Other minerals present were vermiculite, vermiculite with hydroxyaluminium interlayers, chlorite, randomly interstratified chlorite-mica, feldspar, quartz, and trace amounts of amphibole. The amorphous material content varied between 1 and 11% and decreased with increasing particle size. No crystalline iron oxides were detected in untreated clay fractions.